Since the U.S. outbreak of avian influenza A (H5N1) in dairy cattle began in March 2024, dozens of cats are known to have contracted the virus, including barn and feral cats, indoor cats, and big cats in zoos and in the wild (e.g., mountain lions, tigers, leopards, and bobcats). Cats were already known to be susceptible to the H5N1 virus, with several feline cases linked to poultry or wild bird exposure before the outbreak in cattle began.

Cats appear to be particularly susceptible to severe illness, often resulting in death. Whether infected cats can infect other cats is currently unclear; however, that possibility cannot be dismissed. The risk of cat-to-human transmission is considered extremely low, but may increase with prolonged, unprotected exposure to infected animals. Whether direct human-to-cat transmission can occur has not been established, although a recent report of H5N1-infected cats in the households of two dairy farm workers suggests this is possible.

Raw diets: A warning

Unpasteurized milk and raw or undercooked meat—including retail pet diets that contain raw meat—have been linked to severe illness and death from H5N1 in pet cats and captive big cats.

The good news is that infection can be prevented with a few simple practices.

How do cats become infected?
Recent investigations implicate food as a source of infection for cats, most often unpasteurized milk and raw or undercooked meat (e.g., poultry). Other potential sources include:

Raw colostrum and other unpasteurized dairy products (like cream)
Exposure to infected wild birds or poultry
Exposure to infected livestock and their environments
Exposure to people who work on affected farms and to their clothing or other fomites
What are the clinical signs of H5N1 in cats?
Illness may start with loss of appetite, lethargy, and fever, then quickly progress, with cats exhibiting:

Neurologic signs (e.g., ataxia [incoordination], circling, tremors, seizures, or blindness)
Severe depression
Heavy discharge from the nose and eyes
Other respiratory signs, including rapid or difficulty breathing, and possibly sneezing or coughing
What should cat owners do if H5N1 is suspected?
To play it safe, cat owners should:

Call your veterinary clinic—before taking cats in to be seen—and describe any clinical signs you have noticed so that the veterinary team can be ready when the patient arrives.
Limit your cat’s contact with immunocompromised individuals if any exposure to the virus is possible.
Protect yourself and others from influenza by following recommendations from the Centers for Disease Control and Prevention (CDC).
Monitor your family and other animals that might have been exposed for signs of illness, and report any human illness to your local public health official.
What should veterinarians do if H5N1 is suspected?
Veterinarians may suspect a cat has H5N1 from the clinical signs and history. In these cases:

Implement measures to protect yourself and other members of your veterinary team from exposure to the virus. This means:
Avoiding unprotected close or direct physical contact with the cat
Wearing personal protective equipment during sample collection and other interactions with the cat, as described by the CDC. This includes an N95 or more effective respirator, goggles or face shield, gown, gloves, hair or head cover, and rubber boots or shoe covers
Taking particular care during aerosol-generating procedures like swab collection or intubation
Use your clinic’s protocols for isolating and managing patients with suspected zoonotic diseases and practice good environmental infection control. A good resource is the guidelines published by the National Association of State Public Health Veterinarians.
Collect a detailed history from the owner, including the cat’s overall vaccination status, when clinical signs first appeared, possible exposures to known sources of the virus, and whether any other household members (including people and animals) have been ill.
Consider rabies as a differential diagnosis for cats with neurologic signs.
Promptly report the suspected case to your state animal health official, state public health veterinarian, or state veterinary diagnostic laboratory.
Collect samples for submission to a laboratory within the National Animal Health Laboratory Network (NAHLN) that offers highly pathogenic avian influenza PCR testing for cats.
For antemortem detection of the virus in cats, oropharyngeal (preferred) swabs or nasal swabs from both nares are suitable, as are urine, serum, or whole blood samples. Samples should be placed in sterile containers as directed by the laboratory.
Refrain from using rapid in-clinic H5N1 tests, as their accuracy has not been established in cats.
Also consider submitting samples of any raw food the cat has eaten.
If the cat has died, submit the carcass to an NAHLN laboratory for rabies/H5N1 testing.
How can H5N1 infection be prevented in cats?
No vaccine is available yet to protect cats against H5N1. Cat owners and caretakers can help keep their cats safe by following these tips:

Refrain from feeding cats any dairy products or colostrum that have not first been pasteurized or thoroughly cooked to kill the virus.
Thoroughly cook meat before feeding, and avoid feeding raw meat-based treats or diets.
Keep cats indoors to prevent exposure to birds and other wildlife.
Avoid contact with sick or dead birds and other wildlife yourself.
Keep cats away from livestock, poultry, and their environments, especially in areas with known H5N1 outbreaks.
Take steps to prevent contact between captive big cats and wild birds (e.g., cover enclosures with netting and remove bird attractants nearby) in areas where H5N1 is circulating.
Thoroughly wash your hands after handling your cat and after any encounters with poultry, livestock, or wild birds and other animals.
Change your clothes and shoes, and thoroughly wash any exposed skin, after interacting with sick or dead animals that may harbor the H5N1 virus, and before interacting with your cat.
If you feed birds or walk near bird feeders or other places birds (including poultry) gather, change your shoes or disinfect their soles before entering your house.
Immediately contact your veterinarian if you notice signs of H5N1 or think your cat might have been exposed to the virus.